Impaction of the gingival sulcus with elastic bands deforms the gingival sulcus, forming a surface for growth of bacterial plaque, compresses and causes necrosis of surface epithelium and the subjacent lamina propria. The teeth become extruded and make premature contact with their apposing teeth. During mastication, forces applied to extruded teeth probably contribute to their displacement, resulting in their mobility. An inflammatory process commences within 3 days and becomes clinically evident by 7 days. The gingival becomes red-magenta in color and is slightly hemorrhagic. Pockets 4 to 6 min. in depth form within 1 week and remain as long as the impacted substance occupies the space between the tooth and the sulcus epithelium. Removal of the impacted substance results in prompt repair, with complete restoration within 3 weeks. Such repair may be by an epithelial attachment rather than by a fibrous periodontal ligament.